package work01;

        import java.util.Scanner;

/**
 * @author sunlggggg
 * @date 2017/2/27
 */
public class FalutErrorFailure {

    public static double CSta(int[] num){
        //fault
        int length = num.length - 1 ;
        double sum ;
        sum = 0.0 ;
        for(int i = 0 ; i < length ; i ++ ){
            sum += num[i] ;
        }
        return sum * 1.0 / length ;
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int num[] = new int[n];
        for(int i = 0; i < n ; i++ )
            num[i] = scanner.nextInt();
        System.out.println(CSta(num));
    }
}
